In the field of film processors, such as those for x-ray film, a sheet of photosensitive material typically undergoes a number of sequential processing steps; that is, at least one developing step, one fixing step, and a washing operation wherein the photosensitive material is brought into contact with a processing liquid (developer, fixer solution, etc.) to produce a desired chemical interaction with the film substrate or to wash chemical residue away from the substrate surface.
Because it is not desirable to intermix processing fluids of differing chemistries due to their generally antagonistic nature, it has been known to place quantities of different processing fluids in separate, discrete chambers positioned within a processing apparatus.
In processors of the prior art, a sheet of photosensitive material is passed through a series of open topped containers, each containing a quantity of processing fluid, by a series of rollers over a generally sinusoidal transport path into and out of each open topped container. A typical processor of this kind is shown in U.S. Pat. No. 4,994,837.
There are a number of disadvantages with a processor of this type. First, the lengthy transport path impedes the ability to realize a high processing throughput. Exposing a film substrate to atmospheric conditions between processing chambers is not conducive to processability because no chemical interaction takes place during exposure; in other words it is nonproductive, or "dead" time. In addition, the photosensitive material is more susceptible to scratching or marring due to the stresses induced as the material remains in substantial contact with the multiple sets of rollers that are required to traverse a serpentine transport path in a processor of this type.
A number of attempts have been made to deal with the problems described. Processing apparatus using more direct transport paths, extending directly through the walls of adjacent closed tank chambers containing processing liquid have been utilized. In processors of this type photosensitive material enters a chamber partially full of a processing liquid through an opening in the chamber wall, the opening being above the level of the processing liquid that is contained therein. The material is then brought into contact with the processing fluid by either pumping additional processing material into the chamber, thereby raising the level of liquid present in the chamber to contact the passing web, or by downwardly conveying the material to the level of processing liquid. Examples of processors of this type are disclosed in U.S. Pat. Nos. 4,023,190 and 4,142,194.
Processors using methods such as those taught by the preceding examples require exposing the photosensitive material to atmospheric conditions for extended periods, prior to immersion into a processing solution, thereby also affecting the throughput of a processing apparatus.
U.S. Pat. No. 4,987,438 discloses a processor in which a continuous sheet of photosensitive material passes directly through an integrated wall structure positioned to separate adjacent closed containers that are filled with a processing fluid, the wall structure having a pair of parallel, contacting rollers which are rotatably driven and disposed therein. The wall structure is sized to receive the web of photosensitive material, and the rollers act as a transport means for moving the web from and through one processing station to the next adjacent station.
It can be seen that a processing apparatus having a through wall structure as described provides a means for the photosensitive material to traverse a direct transport path by way of rollers already incorporated within the wall structure, without the need for additional rollers or other transport means. However, the processors described require a rather complex sealing means, particularly at the interface where the roller end(s) are attached to either the chamber sidewall or the sidewall of the through-wall structure. To provide an effective seal at this interface is relatively difficult because the rollers must be allowed to rotate to allow the web of photosensitive material to pass therethrough, while also preventing the passage through the ends of processing liquid between adjacent chambers. In order to prevent significant leakage of processing liquid between adjacent chambers separated by a thru-wall structure as described requires that either the roller ends be very tightly manufactured (that is, toleranced on the order of thousandths of an inch) to adequately match the roller ends to the sidewall, or that gasketing or other sealing material be used between the sidewall and the roller end. Both of these measures are quite costly, either due to the preciseness of manufacture in the case of the former, or in terms of frictional effects due to wear of the roller ends against the sealing material requiring periodic changing of the rollers or gasketing. Such frequent replacement is particularly significant with high throughput processors because periodic maintenance is costly in terms of expense and downtime.
Therefore, there is a need to provide an improved thru-wall structure which adequately prevents significant cross-contamination between adjacent processing containers at the sidewall-roller interface which is more reliable, and which is easier to manufacture and maintain than current wall structures used for similar purposes.
There is also a need to provide a sealing means for processors having thru-wall web transports which simplifies the design of the rollers such that the length of the rollers is less significant in the forming of a relatively liquid tight seal, thereby reducing the tightness of tolerancing in the sidewall-roller end interface.